Sections 1 an 2 exam questions
- 1. Sections 1 & 2 Atomic Structure – Periodic Table 2002 Question 5 (a) Define first ionisation energy. (8) (b) Account fully for the trends in first ionisation energies of elements across the second period of the periodic table (i.e. Li to Ne). (15) (c) Account for the trend in first ionisation energies of the elements going down Group II of the periodic table, i.e. the alkaline-earth metals. (6) The approximate values for the first eight ionisation energies of magnesium are given in the following table. (d) Explain why there is an increase in these ionisation energy values. (9) (e) Account for the dramatic increase in ionisation energy going from the second to the third ionisation. Between which two ionisations would you expect the next dramatic increase to occur if the data for further ionisation energies of magnesium were examined? Give a reason for your answer.(12) 2002 Question10. (b) (i) What is the colour of the light associated with the line emission spectrum of sodium? (4) (ii) Explain how line emission spectra occur. 12) (iii) What evidence do line emission spectra provide for the existence of energy levels in atoms? (6) (iv) Why is it possible for line emission spectra to be used to distinguish between different elements? (3) 2002 Question 11. (b) What are alpha-particles (α-particles)? (7) Describe the experiment carried out by Rutherford and his co-workers that led to the discovery of the nucleus. Explain how Rutherford interpreted the results of this experiment to conclude that the atom has a nucleus. (18) 2003 Question 5. (a) Define (i) energy level (ii) atomic orbital. (8) (iii) Write the electronic configuration (s, p, etc.) of nitrogen. (iv) Describe how the electrons are arranged in the orbitals of the highest occupied sublevel of a nitrogen atom in its ground state. (6) (b) Define electronegativity. (6) (i) Describe using dot and cross diagrams the bonding in the water molecule. (9) (ii) What is the shape of the water molecule? Which of the following angles, 104°, 107°, 109°, 120° or 180° would you expect to be closest to the bond angle in the water molecule? Explain your answer. (12) (c) The diagram on the right shows a thin stream of water flowing from a burette. What would you observe if a charged rod was brought close to the thin stream of water? Explain your answer. (9)
- 2. 2003 Question 10.(c) A student was given samples of the following salts: sodium sulfate (Na2SO4) sodium sulfite (Na2SO3) potassium sulfate (K2SO4) (i) What test could be carried out to distinguish between the sodium salts and the potassium salt? (4) What observation would you make in this test? (6) (ii) Describe the test which could be carried out to distinguish between the sulfate salts and the sulfite salt. (15) 2003 Question 11. (b) The diagram shows a sketch of the trend in the first ionisation energies for the elements 3 to 10 in the periodic table. (i) Account for the general increase in ionisation energies across these elements. (7) (ii) Explain why the ionisation energies of element number 4 and 7 are exceptionally high relative to the general trend. (12) (iii) How does the definition of second ionisation energy differ from that of first ionisation energy? (6) 2004 Question 5 (a) Write the electron configuration (s, p, etc.) of the nitrogen atom. (5) Show, using dot and cross diagrams, the bond formation in a nitrogen molecule. Describe the bonding in the nitrogen molecule in terms of sigma (σ) and pi (π) bonding. (9) What type of intermolecular forces would you expect to find in nitrogen gas? Explain your answer.(6) (b) Define first ionisation energy. (9) There is a general increase in first ionisation energy across a period of the periodic table. State the two principal reasons for this trend. (6) The table shows the first and second ionisation energies of nitrogen, oxygen, neon and sodium. Account for the decrease in first ionisation energy between nitrogen and oxygen. Explain why the second ionisation energy of sodium is significantly (about nine times) higher than the first while the increase in the second ionisation energy of neon compared to its first is relatively small (less than twice the first). (15) 2004 Question 10. (b) Describe how Bohr used line emission spectra to explain the existence of energy levels in atoms. (13) (i) Why does each element have a unique line emission spectrum? (6) (ii) The fact that each element has a unique line spectrum forms the basis for an instrumental technique which can be used to detect heavy metals and to measure their concentrations in a soil or a water sample. Name the instrumental technique. (3) (iii) Bohr’s atomic theory was later modified. Give one reason why this theory was updated. (3) 2004 Question 11. (a) Define radioactivity. (i) State two properties of beta (β) particles. (ii) Write an equation for the nuclear reaction involved in the beta decay of 14C (carbon-14). (iii) Explain how the carbon-14 isotope allows certain archaeological discoveries to be dated. 6) (6) (6) (7)
- 3. 2005 Question 10 (b) The minimum energy required to completely remove the most loosely bound electron from a mole of gaseous atoms in their ground state defines an important property of every element. (i) Identify the energy quantity defined above. State the unit used to measure this quantity. (7) (ii) Using X to represent an element, express the definition above in the form of a balanced chemical equation. (6) (iii) Would it take more or less energy to remove the most loosely bound electron from an atom if that electron were not in its ground state? Explain. (6) (iv) An element has a low first ionisation energy value and a low electronegativity value. What does this information tell you about how reactive the element is likely to be, and what is likely to happen to the atoms of the element when they react? (6) 2005 Question 5. (a) What are isotopes? (5) Name the scientist pictured on the right who is credited with the discovery in 1896 that uranium salts emit radiation. (3) Give an example of a radioactive isotope and state one common use made of this isotope. (9) (b) Define atomic radius (covalent radius). (6) Describe and account for the trend in atomic radii (covalent radii) of the elements (i) across the second period, (ii) down any group, of the periodic table. (15) (c) Define covalent bond. (6) Distinguish between a sigma () and a pi () covalent bond. (6) 2006 Question 5. 5. (a) (i) Describe how you would carry out a flame test on a sample of potassium chloride. (8) (ii) Why do different elements have unique atomic spectra? (6) (iii) What instrumental technique is based on the fact that each element has unique atomic spectra? (3) Bohr’s model of the atom explained the existence of energy levels on the basis of atomic spectra. Bohr’s theory was later modified to incorporate the idea of orbitals in recognition of the wave nature of the electron and Heisenberg’s uncertainty principle. (iv) Define atomic orbital. (6) (v) What does Heisenberg’s uncertainty principle say about an electron in an atom? (6) (b) (i) Define electronegativity. (6) (ii) Explain why there is a general increase in electronegativity values across the periods in the periodic table of the elements. (6) (iii) Explain, in terms of the structures of the atoms, the trend in reactivity down Group I (the alkali metal group) of the periodic table. (9) 2006 Question10 (a). (i) What are isotopes? (4) (ii) Define relative atomic mass, Ar. (6) (iii) What is the principle on which the mass spectrometer is based? (9) (iv) Calculate the relative atomic mass of a sample of lithium, given that a mass spectrometer shows that it consists of 7.4 % of 6Li and 92.6 % of 7Li. (6)
- 4. 2007 Question 5. (a) Define energy level. (5) Write the electron configuration (s, p) for the sulfur atom in its ground state, showing the arrangement in atomic orbitals of the highest energy electrons. (6) State how many (i) energy levels, (ii) orbitals, are occupied in a sulfur atom in its ground state. (6) (b) Use electronegativity values (Mathematical Tables p 46) to predict the type of bond expected between hydrogen and sulfur. Write the chemical formula for hydrogen sulfide. Use clear dot and cross diagrams to show the bonding in hydrogen sulfide. (15) Would you expect the hydrogen sulfide molecule to be linear or non-linear in shape? Justify your answer. (6) (c) Hydrogen sulfide has a boiling point of 212.3 K and water has a boiling point of 373 K. Account for the difference in the boiling points of these substances. (6) Would you expect hydrogen sulfide to be soluble in water? Explain your answer. (6) 2007 Question 11. (a) In 1910 Rutherford (pictured right) and his co-workers carried out an experiment in which thin sheets of gold foil were bombarded with alpha particles. The observations made during the experiment led to the discovery of the atomic nucleus. (i) Describe the model of atomic structure which existed immediately prior to this experiment. (7) (ii) In this experiment it was observed that most of the alpha particles went straight through the gold foil. Two other observations were made. State these other observations and explain how each helped Rutherford deduce that the atom has a nucleus. (12) In November 2006 former Soviet agent, Alexander Litvinenko, died in London. The cause of his death was identified as radiation poisoning by polonium-210. (iii) Polonium-210 decays emitting an alpha particle. Copy and complete the equation for the alpha-decay of polonium-210, filling in the values of x (atomic number), y (mass number) and Z (elemental symbol). (6) 2008 Question 5 (a) Define electronegativity (5) (b) State and explain the trend in electronegativity values down the first group in the periodic table of the elements. (9) (c) Use electronegativity values to predict the types of bonding (i) in water, (ii) in methane, (iii) in magnesium chloride. (9) (d) Use dot and cross diagrams to show the formation of bonds in magnesium chloride. (6) (e) Explain the term intermolecular forces. (6) (f) Use your knowledge of intermolecular forces to explain why methane has a very low boiling point (b.p. = –164 ºC). The relative molecular mass of methane is only slightly lower than that of water but the boiling point of water is much higher (b.p. = 100 ºC). Suggest a reason for this. (6) (g) The diagram shows a thin stream of liquid flowing from a burette. A stream of water is deflected towards a positively charged rod whereas a stream of cyclohexane is undeflected. Account for these observations. Explain what would happen in the case of the stream of water if the positively charged rod were replaced by a negatively charged rod. (9)
- 5. 2008 Question 10 (a) (i) Define energy level. (4) (ii) Distinguish between ground state and excited state for the electron in a hydrogen atom. (6) The diagram shows how Bohr related the lines in the hydrogen emission spectrum to the existence of atomic energy levels. (iii) Name the series of lines in the visible part of the line emission spectrum of hydrogen. (3) (iv) Explain how the expression E2 – E1 = hf links the occurrence of the visible lines in the hydrogen spectrum to energy levels in a hydrogen atom. (12) 2009 Question 5 5. (a) Define first ionisation energy of an element. (8) (b) Use the values on page 45 of the Mathematics Tables to plot a graph on graph paper of first ionisation energy versus atomic number for the elements with atomic numbers from 10 to 20 inclusive. (12) (c) Account fully for (i) the general increase in ionisation energy values across the third period of the Periodic Table, (ii) the peaks which occur in your graph at elements 12 and 15, (iii) the sharp decrease in ionisation energy value between elements 18 and 19. (18) (d) Write the s, p electron configuration for the potassium atom. Hence state how many (i) energy sub-levels, (ii) individual orbitals, are occupied by electrons in a potassium atom. Explain why there are electrons in the fourth main energy level of potassium although the third main energy level is incomplete. (12) 2009 Question 11. (c) In 1922, Francis Aston, pictured right, was awarded the Nobel Prize in chemistry for detecting the existence of isotopes using the first mass spectrometer. (i) What are isotopes? (7) (ii) What is the principle of the mass spectrometer? (9) (iii) Calculate, to two decimal places, the relative atomic mass of a sample of neon shown by mass spectrometer to be composed of 90.50% of neon–20 and 9.50% of neon–22. (9)